Fraction calculator

[DTR]

Anybody trying to convince themselves of the simplicity of the imperial system might want to look up how to interconvert mass between troy, avoirdupois, and apothecaries' measure, and how many yards are in a fathom, and how many feet in a rod.

BugBear

Do those conversions come up often in woodworking?

 

[MCB]

Anybody trying to convince themselves of the simplicity of the imperial system might want to look up how to interconvert mass between troy, avoirdupois, and apothecaries' measure, and how many yards are in a fathom, and how many feet in a rod.

BugBear

Do those conversions come up often in woodworking?

What does come up in Woodworking is the need to find the centre of something and to my knowledge, centre rules are only available in inches and NOT in centimetres.

A centre rule is one with zero in the centre and markings increasing both to the right and to the left.

MC

 

[DTR]

I never knew such things existed!

 

[Jacob]

I never knew such things existed!

Nor me.
Centre (or any other division within reason) is very easy to find with dividers, or a marking gauge for centres alone

This should help BB http://gwydir.demon.co.uk/jo/units/length.htm

 

[Sporky McGuffin]

It wasn't "designed" it evolved out of the needs of people working away at real things.

It was based on those units (English Units), but the Imperial system was most certainly designed, and was codified in the 1824 Weights And Measures act.

For example one gallon of pure water at 4 degrees centigrade has a mass of ten pounds

[pedant] Surely a weight of ten pounds? [/pedant]

What does come up in Woodworking is the need to find the centre of something and to my knowledge, centre rules are only available in inches and NOT in centimetres.

I've got a couple of plastic ones - I did find a steel one but only available in Oz. Though a quick Google found these two in the US... possibly worth a group order?

http://www.geionline.com/rulers/center- ... red/1034a/
http://www.totaltools.com.au/toledo-sta ... gGUcpd0esQ

 

[Jacob]

It wasn't "designed" it evolved out of the needs of people working away at real things.

It was based on those units (English Units), but the Imperial system was most certainly designed, and was codified in the 1824 Weights And Measures act.......

Rationalised in 1824 but the design was a lot older! Or did they introduce new units?

 

[Sporky McGuffin]

They changed some definitions - but you're right that the vast majority of units predated the act.

I get the 12 inches thing - as you say, lots of factors - but then there are other units which interrelate by factors of 14 or 16 or 22 - that's just cruel!

Clearly, though, it's possible to build successfully with either system.

 

[bugbear]

This should help BB http://gwydir.demon.co.uk/jo/units/length.htm

Good grief - what a mess.

Of course, each unit makes sense (and is practical) to its specialist user/creator, but the interconversion becomes a worse rat's nest with every units added to the pile.

The sub-divisibility of 12 is (of course) excellent - so for fractions of an inch we use powers of two! :roll:

BugBear

 

[Sporky McGuffin]

I say if we can't have the full SI system let's go furlong/firkin/fortnight as base units. A microfortnight is about 1.2 seconds so it's pretty practical too...

 

[Jacob]

They changed some definitions - but you're right that the vast majority of units predated the act.

I get the 12 inches thing - as you say, lots of factors - but then there are other units which interrelate by factors of 14 or 16 or 22 - that's just cruel!

Clearly, though, it's possible to build successfully with either system.

And there is the baker's dozen. 13 ish
I'm surprised base 20 went out of use - except for the score. Why is that? The french still have quatre vingt. Apparently some foreigners still count eggs in multiples of 20 instead of the more sensible dozen. I wonder what the hens think.

 

[Jacob]

...
The sub-divisibility of 12 is (of course) excellent - so for fractions of an inch we use powers of two! :roll:

BugBear

It's half, and half of that, and half again. Very practical - 1/64" being about the limit of what you can distinguish with the naked eye.

 

[MCB]

Pedants should kindly note that the POUND is a unit of MASS

WEIGHT is a FORCE

The weight of the same mass will vary across the Earth according to the value of “g”

Anybody who studied O-level physics will know all this and more.

With best wishes.

MCB

 

[Phil Pascoe]

Pedants don't need to note it.

 

[Sporky McGuffin]

Pedants should kindly note that the POUND is a unit of MASS

True pedants will know that "pound" can refer to pounds-mass or pounds-force (the gravitational force on one avoirdupois pound-mass at the notional surface of the Earth). Anyone who did GCSE physics would know that.

I don't know if they used to skimp on that sort of thing at school in the distant past. They probably had to keep things simple because the pupils all had smallpox and bubonic plague...

 

[bugbear]

On the beautiful relatedness of units;

1 litre is 1000 cubic centimetres.
1 gallon is 277.42 cubic inches. :roll:

BugBear

 

[Angusdog]

On the vague subject of "Ain't no substitute for cubes" etc, here's a video of a Top Fuel dragster's fuel injector: https://www.youtube.com/watch?v=xGTbQuhhluY

In metric or imperial, that's a lot of petrol (gas). <Note: Might be methanol>